回转式烘干机物料空间运动建模和数值分析

Estimation models and mathematical analysis of particle transportation in a rotary dryer

目前,回转式烘干机筒体内物料运动方式的研究方法主要是建立扬料板持料、撒料模型及物料在筒体内滞留时间模型,但大多数计算公式过于依靠经验常数,且物理意义不明确。本文以物料空间抛落运行机理为基础,采用数值分析法建立了回转式烘干机内的物料运动模型。首先研究了回转式烘干机内物料的空间运动规律,以位于任意回转位置扬料板翼端点处的物料颗粒为研究对象,建立了物料运动模型,并用Matlab绘图工具箱绘制了物料在筒体内运动状态的三维空间图像。然后,推导了物料在筒体轴向运动距离解析式和以扬料板持物量为权重的滞留时间数值分析模型,这些模型综合考虑了干燥介质推力、筒体倾斜度、转速及填充系数等因素的影响,物理意义明确,与生产实例和文献公式计算结果基本一致。

At present, the research method of material movement in the cylinder of a rotary dryer is mainly to set up the held and thrown material models of a lifting plate and the residence time model of materials in the cylinder body. But the most formulas depend too much on the empirical constants, and the physical meaning is not clear. Based on the thrown movement law of materials, the space model of the particle transportation in a rotary dryer is established. First, the motion rule was studied for the solids in the flight rotary dryer. The paths of fall of the particles in the drum were drawn by Matlab drawing toolbox and showed on the three-dimensional image. Then, the analytic mathematical models of the motion were proposed for the space particle. The equations of residence times were deduced. The proposed estimation models were determined by considering the air drag on the solids in the drum, as well as the inclined angle, the rotation speed and the filling rate of a drum. The calculation formula of residence times was with a clear and definite physical meaning. The residence time calculated by using the proposed equation was compared to the average experimental values from the engineering example and the results obtained by calculations using equations proposed in the literature. The equation proposed for predicting residence time generated accurate estimations.